Apparatus for grinding rock bit inserts

ABSTRACT

Apparatus for grinding inserts in the head of a rock drill bit uses a cup shaped grinding wheel having a planar lip; the bit is held in a vice and the planar lip is movable across the insert and also to a limited extent into the insert, which limitation is effected by incorporating a spring acting against the support. The grinding wheel is vibrated during the grinding process.

United States Patent 91 [21] App1.No.:401,621

[52] US. Cl 51/54; 51/126; 51/166 FB; 269/132 [51] Int. Cl B24b 3/33; B23q 3/06 [58] Field of Search 51/32, 54, 55, 56, 126, 51/166 TS, 166 PB; 269/132 [56] References Cited UNITED STATES PATENTS 115,068 5/1871 Lane 51/126 X 515,801 3/1894 Spaulding 51/126 1,054,662 3/1913 Amborn 269/132 MacSween 1 June 10, 1975 [54] APPARATUS FOR GRINDING ROCK BIT 1,179,850 4/1916 Lingo 51/225 INSERTS 2,055,361 9/1936 Oliver 51/32 X 2,751,718 6/1956 Falkman et a1. 51/32 [76] Inventor: George MacSween, 161 Bridgeland 2,849,839 9/1958 Lofqvish etal 51/55 7 Ave., Toronto, 390 Ontario, Canada 3,451,171 6/1969 Coes 51/99 22] Filed: Sept. 28, 1973 Primary Examiner-Donald G. Kelly Assistant ExaminerK. J. Ramsey Attorney, Agent, or Firm-C. C. Kent; K. M. Hill [57] ABSTRACT Apparatus for grinding inserts in the head of a rock drill bit uses a cup shaped grinding wheel having a planar lip; the bit is held in a vice and the planar lip is movable across the insert and also to a limited extent into the insert, which limitation is effected by incorporating a spring acting against the support. The grinding wheel is vibrated during the grinding process.

5 Claims, 5 Drawing Figures APPARATUS FOR GRINDING ROCK BIT INSERTS This invention relates to grinding apparatus which has particular, but not exclusive, use for sharpening cutting inserts located in the head of a rock bit body.

A popular type of drill bit is constructed of a solid steel body having a working face at one end with a plurality of wear resistant tungstan carbide inserts which are mounted in pairs to form an in-line cutting edge; these inserts are then ground to subtend a specific angle which is usually l l. The cutting edge of the inserts is blunted in use. more particularly at the outer edge, and they are re-ground at intervals with the hardness of the rock being drilled.

Re-grinding has been done manually but to achieve the desired cutting edge a great deal of care is necessary and the process often consumes more time than the drilling. In an attempt to overcome this problem apparatus has been developed in which a disc-shaped grinding wheel tapered toward the perimeter is used to grind two inserts at the same time. One problem in its use is to control the amount of abrasive which is removed, another is that a great deal of heat is evolved and again the difference in speed of the grinding surface leads to unevenness across the face of the insert.

It is an object of the invention to provide apparatus for grinding inserts located in the head of a rock drill bit, accurately and quickly without undue removal of the surface of the insert.

It is a further object of the invention to provide apparatus for grinding rock drill bit inserts whereby the production of heat will be largely eliminated.

In a preferred embodiment the apparatus includes a cup shaped grinding wheel, the lip of which provides a planar surface. The body of the rock drill is held by an adjustable support at an angle to the vertical so that on rotation of the bit one surface of the V-shaped inserts which are in line may be brought into contact with the planar edge. The grinding wheel is held by a support which provides for movement of the planar edge across one surface of the insert and also for limited movement into the insert when grinding is in progress. This limited movement is achieved by including biasing means acting against the support. The apparatus also includes vibrating means which acts on the support for the grinding wheel while grinding is in progress. The vibrating means has the effect of practically eliminating the production of heat during grinding.

The invention will now be described in relation to the accompanying drawings in which:

FIG. 1 is a perspective view of a preferred embodi ment of apparatus constructed according to the inventron.

FIG. 2 is a plan illustrating the grinding position of the cup-shaped wheel incorporated in the apparatus illustrated in FIG. 1.

FIG. 3 is a section taken on the lines 33 of FIG. I.

FIG. 4 is a section taken on the lines 44 of FIG. 1.

FIG. 5 is a section taken on the lines 5-5 of FIG. 4.

In the description like numbers represent like parts. The apparatus is carried on an adjustable stand generally denoted by the numeral I0 consisting of arms 12 each pivotally secured by a ball bearing 14 contained in a pad 16. The upper end of each arm 12 is pivotably secured between a pair of abutments I8 welded to a collar 20. The stand provides, in well known manner, for firm positioning on uneven terrain since the apparatus is also intended to be used in the drilling field.

The collar 20 is attached to the lower end of an upwardly disposed tubular mount or column 22.

Above the collar 20 and spaced therefrom is another collar 24 which is slidable on the mount 22 and secured thereto on inward rotation of a key 26.

Extending from the collar is an arm 28, the outer end of which terminates in a casing 30. A rod 32 with a vertical row of teeth 34 extends through the casing 30 in sliding relationship and in well known manner. A gear not shown is located in the casing 30 which gear engages the teeth 34, being operable by handle 36 to alter the vertical position of the rod 32.

A holder generally denoted by the numeral 38 is se cured to the upper end of the rod 32. The holder 38 secures in releasable manner, a rock drill bit generally denoted by the numeral 40. As shown more particularly in FIG. 5, the holder 38 includes an inclined base plate 42, the underside of which is welded to the upper end of the rod 32. Integral with the base plate 42 is a normally disposed side plate 44.

A top plate 46 is secured to the upper edge of the side plate 44 by bolts 48. The top plate 46 has an aperture which is somewhat larger in diameter than the bit so that the latter can be dropped into the holder 38 with the base of the shank 50 of the bit 40 resting on the base plate 42. The top plate 46 and the base plate 42 are secured together by an U-shaped bracket 52.

Extending into the holder 38 below the top plate 46 and secured to the side plate 44 as shown in FIG. 5 are a pair of spaced apart abutments 54 each having toothed arcuate portions 56 illustrated more particularly in FIG. 4. A slotted cylindrical member 58 is contained in the holder 38. The base of the member 58 lies on the base plate 42 and the slot 60 of the member 58 is slightly wider than the width of the arcuate portions 56 of the abutments 54.

Diametrically opposed to the slot 60 are a pair of spaced apart eye bolts 62 integral with and extending outwardly of the cylindrical member 58. The bracket 52 also has a pair of spaced apart eye bolts 64 but these are threaded into the bracket 52 and provided with adjusting nuts 66. Each eye bolt 66 is attached to an individual spring 68, the other end of which is attached to one of the eye bolts 64, the springs 68 thereby being substantially parallel.

Positioned between the upper and lower eye bolts 62 and bearing against the cylindrical member 58 is a chain link 70, the ends of which are secured to bolts 72 which slidingly traverse the side plate 44. Each bolt 72 is threaded into an individual abutment 74 spaced from the outside of the side plate 44. The abutments 74 are connected by a rotatable rod 76 held in position through nuts 78.

The mid portion of the rod 76 between the spaced apart abutments 74 carries in fixed relation a cam 80 which co-acts with a block 82 secured to the outward face of the side plate 44. The cam 80 is operable by a handle 84. The holder 38 forms a chain vice for the bit 40. Movement of the cam 80 will cause the cylindrical member 58 to slide over the toothed abutments 74 which enter the slot 60. As a result the shank 50 of the bit body 40 is held firmly against the toothed abutment 74.

The bit 40 shown in FIG. 1 has four inserts 86, each exhibiting a pair of surfaces 88 which provide a cutting edge 90. The inserts 86 are shown as disposed in spaced apart pairs with the cutting edge 90 of each pair in line. This type of bit has wide application in the field and while the apparatus constructed according to the in vention is not confined to shaping this particular type of bit, it has particular application thereto because the surfaces on the same side of each pair of inserts in nine may be ground without changing the position of the bit in the holder. To ac ieve this end the base plate 42 of the holder 38 is inclined to the vertical at an angle which is half that subtended by the surfaces 88 which define the cutting edge 90 of each insert 86. As already stated. these surfaces generally subtend 1 and hence the inclination of the base plate 42 will be at an angle of 55 to the vertical.

A grinding head generally denoted by the numeral 92 is carried on the column 22 through an adjustable collar 94 secured in position by a key 96. The collar 94 has a pair of abutments 98 which support a rotatable bar 100 held in place by nuts 102 threaded on the end of the bar 100.

A pair of struts 104 extend outwards in relation to the column 22 from the bar 100. The struts 104 terminate in a sleeve 106 in which is located a rotatable rod 108 secured to a collar 110 which rests on the upper edge of the sleeve 106. The collar 110 has a pair of abutments 112 traversed by a pin 114 which carries a block 116 pivotable on the pin 114 in a vertical plane.

Welded to the block 116 is a support arm 118 to which is bolted a vibrator element 120.

The end of the support arm 118 removed from the pivotable block 116 carries a casing 123 which contains the drive, not illustrated, for a cup shaped grinding whee] 122 disposed as shown with a planar lip 124 facing downwards. The casing 123 has a handle 126.

It will be appreciated that the grinding wheel 122 has unlimited movement in the horizontal plane when the handle 126 is manually operated because rotation may be effected at the two locations indicated by the arrows in FIG. 1.

Also it may be lifted in the vertical plane on pivotal movement of the block 116. However downward movement is iimited during the grinding operation as described hereunder. To effect this a plate 128 with an open ended slot 130 is welded to the underside of the support arm 118. An end portion of a rod 132 is located in the open ended slot 130 and the other end of the rod 132 is secured to the lower end of the rod 108 located in the sleeve 106. A spring 134 surrounds the rod 132. the spring 134 bearing against the slotted plate 128. A stop 136 is provided to adjust the pressure of the spring 134 on the plate 128. This is arranged so that downward pressure by the handle 126 is resisted to the point where the pivoted block 116 stops short of its contact with the sleeve 106. As indicated more particularly in HO. 3 the planar Z p 124 of the grinding wheel 122 is slightly inclined to the horizontal, by way of example and not limitation this may be something of the order of li'32nd of an inch at the outer side of the grinding wheel 122. Accordingly when the grinding wheel is depressed by operation of the handle 126 the planar lip 124 of the grinding wheel [22 assumes a substantially horizontal position.

To operate the apparatus lln; hit 40 is placed in the holder 38 and the": rotated by hand until a pair of inscrts 86 are positioned so that a pair of surfaces 88 in line are in the substantially horizontal position. The chain vice is then tightened and one of the surfaces 88 brought into contact with the planar lip 124 on the grinding wheel 122 through manipulation of the ban dles 36 and 126.

The grinding wheel 122 which is shown as operable by air lines 140 is then activated along with the vibrator grinding pressure is exerted by the handle 126 to effect the controlled removal of material from the surfaces 88 of insert 86, the grinding wheel being movable across the corresponding surfaces of both inserts as illustrated in FIG. 2.

Both the grinding wheel and the vibrator are shown as operable through air lines but it will be appreciated that other means could be employed; also various forms of vibrators acting on the grinding wheel 122 could be utilised.

What is claimed is:

1. Apparatus for grinding the surface of an insert located at one end of a rock drill bit body comprising means for holding said body to locate said insert in a predetermined position, a driven cup shaped grinding wheel having a planar lip, moveable support means for said wheel comprising a first transversely rotatable arm and a second transversely rotatable arm rotatable with respect to said first arm, said grinding wheel being located on said second arm, whereby said planar lip of said grinding wheel is transversely moveable across said insert during grinding; and means acting between said support means providing limited movement of said planar lip into said insert, comprising a member pivoted on said first arm about a transverse axis and secured to said second arm, stop means on said first arm, and biasing means supported by said first arm urging said member away from said stop.

2. Apparatus according to claim 1 wherein said stop means is positioned whereby manual pressure on said second arm against the action of said biasing means brings said planar lip into a substantially horizontal position in grinding contact with said insert surface, and wherein said means for holding said body includes a base bracket for supporting a cylindrical member.

3. Apparatus according to claim 1 having means vibrating said grinding wheel during grinding and wherein said bracket base supports a cylindrical member, said bit body being located therein, toothed abutments in said bracket, chain means around said cylindrical member and means acting on said chain means to move said cylindrical member whereby said bit body engages said toothed abutments.

4. Apparatus according to claim 3, wherein said cylindrical member has a vertical slot wider than said toothed abutments to receive same when said cylindrical member is activated by said chain means.

5. Apparatus according to claim 3, having means acting on said cylindrical member to disengage it from said toothed abutments on release of said chain means. 

1. Apparatus for grinding the surface of an insert located at one end of a rock drill bit body comprising means for holding said body to locate said insert in a predetermined position, a driven cup shaped grinding wheel having a planar lip, moveable support means for said wheel comprising a first transversely rotatable arm and a second transversely rotatable arm rotatable with respect to said first arm, said grinding wheel being located on said second arm, whereby said planar lip of said grinding wheel is transversely moveable across said insert during grinding; and means acting between said support means providing limited movement of said planar lip into said insert, comprising a member pivoted on said first arm about a transverse axis and secured to said second arm, stop means on said first arm, and biasing means supported by said first arm urging said member away from said stop.
 2. Apparatus according to claim 1 wherein said stop means is positioned whereby manual pressure on said second arm against the action of said biasing means brings said planar lip into a substantially horizontal position in grinding contact with said insert surface, and wherein said means for holding said body includes a base bracket for supporting a cylindrical member.
 3. Apparatus according to claim 1 having means vibrating said grinding wheel during grinding and wherein said bracket base supports a cylindrical member, said bit body being located therein, toothed abutments in said bracket, chain means around said cylindrical member and means acting on said chain means to move said cylindrical member whereby said bit body engages said toothed abutments.
 4. Apparatus according to claim 3, wherein said cylindrical member has a vertical slot wider than said toothed abutments to receive same when said cylindrical member is activated by said chain means.
 5. Apparatus according to claim 3, having means acting on said cylindrical member to disengage it from said toothed abutments on release of said chain means. 